Slab and Item for a diagonal block in tekla

When I use the Slab command in grass, Tekla displays a diagonal block.
But when I use the Item command in grass, Tekla displays an entire rectangular block
I want to turn it off, is there any way? Thank you everyone
( Illustrative images only)


You probably need to provide more info order for anyone to be able to help you. Scrip, curve outline anything.